At some point during any immersion or wet processing operation, the object being processed is separated from its liquid bath. This may occur many times depending on such process and device at intermediate or final stages of processing. Such may occur in one or more immersion vessels as sequential steps or separated by other different process steps. As a general matter, and depending of the process, it may be desirable to rinse an object for cleaning it after being subjected to processing fluid in order to remove any contaminants or residual processing fluid. Moreover, the object may be further dried to remove any processing or rinsing liquids and to provide a clean processed object.
In the case of processing microelectronic devices, such as those including semiconductor wafers and microelectronic devices at any of various stages of processing, flat panel displays, micro-electrical-mechanical-systems (MEMS), advanced electrical interconnect systems, optical components and devices, components of mass data storage devices (disk drives), and the like, cleanliness is critical in virtually all processing aspects. Representative steps in immersion processing of microelectronic devices include microelectronic device etching and rinsing. As used herein, immersion processing means a process where at least a portion of a device, such as a microelectronic device, is subjected to immersion for a period of time for any effective purpose.
One important aspect in providing clean microelectronic devices after immersion processing is to start with the use of clean processing liquids. Clean liquid use can be controlled by known or developed filtering processes so as to minimize introduction of contaminants into the processing environment. This is particularly true where devices are being cleaned or rinsed by an immersion process, such as by using deionized water (DI water) as a rinsing liquid as either flowing or non-flowing liquid bath. Specific filtering techniques for ultra-clean DI water have been developed for use in the microelectronic industry, such as those described in U.S. Pat. Nos. 5,542,441, 5,651,379 and 6,312,597 to Mohindra et al. Microelectronic devices are often rinsed within vessels as a batch or individually by flowing DI water across device surfaces as supported within the vessel and cascading the DI water from the vessel. Such a process vessel for microelectronic device rinsing is commonly referred to as a cascade rinser. Cascade rinsing typically utilizes an immersion vessel having inner and outer chambers that are separated from one another by a partition or weir. One or more devices are positioned within the inner chamber of the immersion vessel. Rinse liquid, such as DI water, is supplied to the inner chamber from a source even after the inner chamber is filled. For some desired period of time then, the rinse liquid overflows and cascades over the weir into the outer chamber. That way contaminants that may be dislodged and/or residual process fluid desirably flow with the cascaded liquid from the inner chamber and away from the devices.
It is also just as important to prevent contamination or recontamination to a surface of a microelectronic device, as such contaminant may be present in the processing liquid as a result of being supplied within the process liquid, as previously dislodged from a device surface, or as a result of the device processing (including previously used processing liquids or other liquid contaminants). This is particularly true when separating the microelectronic device(s) from the liquid bath so that no substantial surface contamination occurs from contaminants that may be suspended within the rinse or other processing liquid. Microelectronic devices may be separated from any liquid bath by lifting the devices from the bath or draining the liquid bath, or a combination of the two. During such separation, contaminants that may be near a device surface during separation can sometimes be deposited onto a device surface depending on surface and particle features, affinities and sizes.
Regardless of the mechanisms involved, the basic step of separation may simply be characterized as the controlled replacement of a liquid environment about an object or portion thereof with a gas environment. As a result, the object or portion thereof is separated from the liquid. In an inline process, separation is typically done by replacing one fluid that is supplied inline with a subsequent fluid (e.g., changing from rinse liquid to clean gas). See, for example, U.S. Pat. Nos. 4,984,597 and 4,911,761 to McConnell et al. For a liquid bath type immersion process (i.e., where one or more microelectronic devices are supported or suspended within liquid contained by a vessel), the liquid environment can be controllably replaced with a gas environment by lifting or draining, as above.
In order to enhance this separation step, processes have been developed that introduce a substance within the gas environment during the replacement stage about an object that causes the liquid to shed more easily from the object surfaces. By shedding the liquid better, there is less a likelihood that any contaminant would be deposited onto an object surface from the liquid, and there is an increased chance to remove any such contaminant from an object surface. Developed processes utilize isopropyl-alcohol (IPA), in particular, to take advantage of what is known as the Marongoni effect to create a gradient in the concentration of the IPA mixed with the liquid at or near the liquid/gas meniscus formed at the object surfaces. The concentration gradient causes an acceleration of the liquid from an object surface as liquid having a greater concentration of the IPA within such a meniscus has an increased tendency to flow toward a more dilute mixture of IPA within the liquid bath. Many processes and systems have been developed taking advantage to various degrees such Marongoni effect to enhance rinsing and cleaning of microelectronic devices.
In particular, certain apparatuses and methods have been developed as are described with U.S. Pat. No. 5,772,784 to Mohindra et al, and which is owned by the assignee of the present invention. Described processes steps include the introduction of IPA as a cleaning enhance substance within a carrier gas stream for delivering a dilute concentration of IPA within the gas environment as it replaces the liquid environment caused by draining the immersion vessel. The IPA is relied upon, as described above, to increase the tendency of the liquid to flow from object surfaces during the step of separating the object(s) from the liquid.
Whereas the main goal of separation is to leave clean device surfaces, the separation step itself, however, does not necessarily result in dry devices. That is, after a rinsing step, a separate drying step may be performed to dry liquid drops or films that may still be present. A particular drying operation utilized depends on parameters of the separation (e.g. speed of separation, orientation of the microelectronic devices, and the like) as well as characteristics of the microelectronic devices themselves (e.g. the hydrophilic or hydrophobic nature of the device surface). Any liquid droplets or films that remain on a microelectronic device surface after separation, such as may result at or near contact points with support structure or as minute droplets or films that hold to the microelectronic device surface, are desirably removed from the microelectronic device surface. If such droplets or films are left to evaporate from the microelectronic device surface, any contaminants within the droplets or films can be deposited on the microelectronic device surface, which contaminants may render a portion of the microelectronic device unsuitable for further processing or use. Known drying techniques include the use of heated gases, such as heated nitrogen gas, after the rinsing step for removing unwanted droplets and films from the microelectronic device surfaces.